Workers in the art of designing and/or using printed circuit boards recognize that there are many problems associated with mounting plug-in devices on the boards to be in electrical connection therewith. At times (in simplest form) the male pins for devices, such as device D in FIG. 1, are simply soldered into a plated female hole contact, (e.g. like contact f-c' in printed circuit board P.). More usually, and in the more complex situations, an intermediate connector means is employed, e.g., like connector assembly C in FIG. 1. Connector C will be recognized as comprising a plastic housing with an array of female contacts f-c dimensioned and positioned to receive male pins mp of one or several devices D in conductive (removable) engagement. Connector C will itself typically present connector means such as projecting connector pins c-p which may in turn be mounted in associated printed circuit board PB (note solder joints S fused around pins c-p). In such an instance the female-male connectors of assembly C are soldered to the PC board PB, then the male pins of header D are mated to contacts f-c.
Thus, the cross-section shown in FIG. 1 illustrates a typical pin grid array (PGA) connector known to workers today (female-male type). Workers appreciate the limitations of such a PGA connector, for instance, presenting an undesirably low pin density and an undesirably high profile, or height (see height Ht typically about 360-400 mils). Typical pin density is a 0.1 by 0.1 inch grid.
To scale-down this design to accommodate a higher density pin grid (0.05 by 0.05 inches, or less, is desirable now), conventional connectors--when designed to accommodate state of the art manufacturing tolerances-- are commonly 0.3 inches or more in height, with a current-conducting path length L.sub.c which is necessarily greater than their height (e.g. as with spring contacts f-c in FIG. 1--and unlike our invention e.g. as in FIG. 2A). This length L.sub.c must be minimized in an effective high speed circuit, or else the impedance along this path must be controlled. Reliability is commonly compromised, at such high pin density, the pins must become small and fragile--and so cannot sustain enough pin-mating force to break through the corrosion that typically forms on the contacts.
It is an object of this invention to provide a superior connector of the "two-faced-female" type, presenting a smaller height (lower profile; e.g. about 0.2" in some cases), accommodating a higher pin grid density (e.g. on the order of 0.05 by 0.05 inches or less), as well as having greater pin mating force to break through such corrosion (e.g., need for the order of 100 grams nominal force, 85 grams minimum; vs. the more typical 30 grams nominal, 20 grams minimum force with typical known comparable pins and connectors today).
Workers realize that a "low profile" typically reduces conductive path length and introduces associated impedance mismatch, thus accommodating high speed devices.
Workers will also recognize that a connector C as in FIG. 1 is relatively costly and complex, requiring complex stamped parts such as the female contacts f-c (which involve low-spring-force connectors which are necessarily long) and which can give rise to impedance mismatch with high frequency high speed circuits. They also involve connections for pins mp with contacts f-c characterized by as few as one or two "point-contacts"; such point-contacts can be interrupted, giving rise to a break in the electrical circuit involved (e.g., interposition of corrosion, dirt or the like on one or both sides of a pin in a female contact, as workers recognize). For increased reliability such contact-corrosion or interruption must be avoided, or broken-through; otherwise intermittent circuit interruption results.
Another very serious defect is that when conventional contacts are soldered to a PC board, the unit becomes impractical to rework or field-fix (soldered connections should be avoided for this reason). Another object of this invention is to avoid the above difficulties and accommodate rework and field-fix, while avoiding soldered connections. Workers disfavor soldered connections when working with large pin arrays because of "hidden" solder joints--these can't be visually inspected, thus their integrity/reliability remains in question. Removal or rework of a pin grid array is difficult.
The present invention further avoids circuit interruption from interposed dirt or corrosion, etc., by featuring self-wiping contacts and contacts featuring "three-point ohmic connection". The connector of the subject invention is also adaptable to virtually any design of PC boards or plug-in device.
The invention also preferably involves a connector characterized by low insertion force LIF in one case and a zero insertion force ZIF in other cases. In many instances, LIF is achieved by mating only one-half the male pins at a time (with female contacts--the first half entering with ZIF).
In a preferred feature, connectors according to this invention involve insertion of pins from the plug-in devices on one side and from the PC board on the other side--with lateral resilient ohmic gripping means engaging paired ones of these (PC/plug-in) pins. This gripping means is adapted to be resiliently spread by insertion of such paired pins (at least one thereof) and to urge the pins against one another, in ohmic wiping contact with one another and with the gripping means. This gripping means preferably involves one or several resilient contact-segments, and, in a particular preferred case, takes the form of an open-ring-clip with extended lever arm (e.g., see FIGS. 5, 6 and 7 described below).
Workers are also aware of the problem of "creep", whereby a surrounding plastic housing supporting a metallic female contact, like f-c, is at times thrust outward and away from its reference support position. "Creep" is caused by reaction forces from a female contact as transmitted to a surrounding plastic support. Such creep is exaggerated in high temperature environments and is common in ZIF connectors.
In a variation of FIG. 1, a manually operable cam means is also provided to force-open such female contacts until the associated male pins are inserted with zero force (ZIF) therein, whereupon the cam means is "moved", allowing the resilient contacts to close tightly against their pins.
It is an object hereof to address at least some of the afore-suggested problems, provide at least some of the afore-referenced features, and in general provide improved connector means.